frame:add-snip-menu-items in Framework Functions

• (frame:add-snip-menu-items menu menu-item%) -> void?
     menu : (is-a?/c menu%)
     menu-item% : (subclass?/c menu-item%)

  Inserts three menu items into menu, one that inserts a text box, one that inserts a pasteboard box, and one that inserts an image into the currently focused editor (if there is one). Uses menu-item% as the class for the menu items.